Remove dead return path from JSObject::GetHiddenPropertiesHashTable.

R=verwaest@chromium.org, rafaelw@chromium.org
TEST=cctest/test-api

Review URL: https://codereview.chromium.org/57783002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17456 ce2b1a6d-e550-0410-aec6-3dcde31c8c00